New catalyst controls activation of a carbon-hydrogen bond

A side view of the new catalyst. The dirhodium, shown in blue, "is the engine that makes the catalyst work," says Emory chemist Huw Davies. "The shape of the scaffold around the dirhodium is what controls which C-H bond the catalyst works on." Graphic image by Kuangbiao Liao.

Chemists have developed another catalyst that can selectively activate a carbon-hydrogen bond, part of an ongoing strategy to revolutionize the field of organic synthesis and open up new chemical space.

The journal Nature is publishing the work by chemists at Emory University, following on their development of a similar catalyst last year. Both of the catalysts are able to selectively functionalize the unreactive carbon-hydrogen (C-H) bonds of an alkane without using a directing group, while also maintaining virtually full control of site selectivity and the three-dimensional shape of the molecules produced.

“Alkanes have a lot of C-H bonds and we showed last year that we can bring in one of our catalysts and pluck out a particular one of these bonds and make it reactive,” says Huw Davies, an Emory professor of organic chemistry whose lab led the research. “Now we are reporting a second catalyst that can do the same thing with another C-H bond. We’re building up the toolbox, and we’ve got more catalysts in the pipeline that will continue to expand the toolbox for this new way of doing chemistry.”

Selective C-H functionalization holds particular promise for the pharmaceutical industry, Davies adds. “It’s such a new strategy for making chemical compounds that it will opens up new chemical space and the possibility of making new classes of drugs that have never been made before.”

Alkanes are the simplest of molecules, consisting only of hydrogen and carbon atoms. They are cheap and plentiful. Until the recent development of the catalysts by the Davies lab, however, alkanes were considered non-functional, or unreactive, except in uncontrollable situations such as when they were burning.

The first author of the Nature paper is Emory chemistry graduate student Kuangbiao Liao.